1. Field of the Invention
The present invention relates to a method and apparatus for regulating the composition of a fuel air mixture supplied to an internal combustion engine.
2. Description of the Prior Art
It is known that the composition of the mixture of fuel and air supplied to internal combustion engines can be adjusted by means of a secondary air inlet in the intake pipe, this air inlet being controlled by a valve which is completely or partly controlled by information supplied from a detector which measures the oxygen content (or CO content) or more generally the composition of the exhaust gas.
The practical realization of such devices, however, poses complex problems. An internal combustion engine operates over a wide range of outputs depending mainly on its speed of rotation and above all on the intake pressure. It follows that a regulating system must respond equally over a considerable output range to ensure that it will make the necessary correction no matter what the engine output while at the same time remaining sufficiently sensitive to respond with high precision, and its response time must also be compatible with the engine speed.
Such a system must ensure an accuracy of regulation with a percentage of error below 2%.
Furthermore, the introduction of secondary air as a regulating factor must not affect the homogeneity of the mixture, otherwise it would impair complete combustion in the cylinders of the engine.